A secret organisation called The Outfit recruits and trains civilians, sending them undercover to aid in the war effort, or placing them in administrative tasks to aid the group. Each person arrives at The Outfit by a different route: Mathilde ('Matty') escaped to London from France and wants desperately to contribute to the war effort; Liz, whose husband is serving overseas and whose brother has just died in the war, stumbles into the group almost by accident. Former actor Colin Beale also trains for undercover work. Vivien's husband was executed when his work with The Outfit was uncovered. But they all come together against the common enemy.